A fastener (10) for securing a panel (12) to a substrate (14) is disclosed. The fastener (10) has a body portion (18) that is received in the substrate (14) and a pin portion (16) that is passed through the panel (12) and is driven into the body (18) to secure the panel (12) to the substrate (14). The body (18) has a pair of legs (45) that act to retain it within the substrate (14) and which incorporate an interference control mechanism (50) that controls the force required to insert the pin (16) into the body (18). The interference control mechanism (50) may include a bore (52) formed through the legs (45), a reduced cross-sectional area (54) of the legs (45) or an elastomeric member (56) molded onto the legs (45). <IMAGE>